采用分段线性补偿的基准电流源设计

介绍了一种高精度基准电流源.首先设计出不同温度系数的电流IPATA和IVBE的产生电路,然后分析线性补偿的基本原理,通过电流的减法运算,在整个温度范围内分两段产生不同的补偿电流INL,并完成对电流IPATA的分段线性补偿,从而获得温度系数较低的带隙基准电流源.仿真结果表明:在-42℃～120℃的温度范围内,该电路输出基准电流的温度系数小于10-5/℃.     

On Multiscroll Chaotic Attractors in Hysteresis-Based Piecewise-Linear Systems

This brief analyzes the multi scroll chaotic attractors in hysteresis-based piecewise-linear systems. The dynamics of the chaotic attractors are first analyzed. The unstable limit cycles and the boundary conditions for the occurrences of chaotic behaviors are derived. The sensitivity of systems parameters on the chaotic behaviors is also studied, accompanied by a number of simulations.     

基于核函数正则变换的HRRP识别法

雷达高分辨距离像包含了目标的结构信息,在雷达目标识别领域有良好的应用前景.应用核函数的分类方法有很强的泛化能力,本文将核函数的思想引入正则变换,提出核函数正则变换,该变换能在考虑各类样本整体和个别特性的同时提取非线性特征,将其与线性支持向量机结合实现目标分类.用实测数据仿真实验,验证了所提方法的有效性.     

基于核函数正则变换的HRRP识别法

雷达高分辨距离像包含了目标的结构信息,在雷达目标识别领域有良好的应用前景.应用核函数的分类方法有很强的泛化能力,本文将核函数的思想引入正则变换,提出核函数正则变换,该变换能在考虑各类样本整体和个别特性的同时提取非线性特征,将其与线性支持向量机结合实现目标分类.用实测数据仿真实验,验证了所提方法的有效性.     

Chaotic Negative-Resistance Oscillators with a Multibranch Piecewise-Linear Current—Voltage Characteristic

Chaotic oscillators with a negative-differential-resistance (NDR) subsystem having a multibranch piecewise-linear i–v characteristic (IVC) are considered. The problem of switching between chaotic oscillation regimes by changing the IVC electronically is addressed. New circuit realizations of the NDR subsystem are described in detail. It is shown that they provide highly stable IVCs.     

A New Chebyshev-like Low-pass Filter Approximation

A new Chebyshev-like low-pass filter approximation is proposed for which the order is always odd and hence there is no problem for doubly terminated LC ladder realization. Flexibility of shaping the response and lower Q values of complex poles appear to be the major advantages of the new approximation as compared to the normal Chebyshev filter.     

一种采用非均匀量化的近似Log-MAP算法

为了简化Log-MAP算法、减小其硬件查表实现时所占用的外存储单元,采用了非均匀量化的方法分别对Log-MAP算法中的校正函数进行两电平和五电平近似,从而得到相应的量化函数。并将该量化函数用于LTE Turbo译码器,在AWGN信道上进行软迭代译码仿真。仿真结果表明,两电平和五电平非均匀量化的近似Log-MAP算法将Max-Log-MAP算法的译码性能提高了0.2～0.3 dB,与原Log-MAP算法性能接近,但却能大大减少查表时需要检索的数据量。     

Piecewise-Linear Identification of Nonlinear Dynamical Systems in View of Their Circuit Implementations

We address here an aspect of the problem concerning circuit implementations of nonlinear dynamical systems that depend on control parameters. In particular, the problem of the identification of such systems is addressed in two steps. The first step uses the state-space reconstruction (through time delay reconstruction associated with principal component analysis) on the basis of scalar time series measured in the systems to be identified. The second step deals with the approximation of the flow in the reconstructed space (through a piecewise-linear approximation technique). The proposed method is first validated with two examples concerning known systems and then applied successfully to two realistic cases.     

A Chebyshev Approximation Method for Microstrip Problems

The quasi-static TEM mode of a microstrip line may be obtained approximately from the solution of Laplace's equation subject to certain boundary conditions. The Green's function approach leads to the solution of a Fredholm integral equation with a logarithmic singularity in the kernel. It is shown that if the charge distribution on the strip is expanded in terms of Chebyshev polynomials then the integrals arising from the logarithmic term may be evaluated in closed from, and the integral equation may be approximated closely by a set of algebraic equations. The method is applied to numerous open and shielded configurations of strips and couple-strips in the presence of dielectrics. Numerical results are compared with exact results whenever possible and with results from previous authors. Design curves are presented for particular shielded couple-strip configurations.     

一款10位逐次逼近型模数转换器设计

基于0.18μm CMOS工艺设计一款10位逐次逼近型模数转换器(SAR ADC),采用了阻容混合型的数模转换器(DAC)以实现面积与性能上的折衷,高位采用温度码设计以提高DAC的线性度。采用了失调电压较小的静态比较器结构,通过在DAC和比较器之间加入了高增益的前置放大器来消除比较器失调电压对ADC性能所带来的影响。仿真结果表明:在电源电压为2.8 V、采样速率为116 k S/s、输入信号频率约为57 k Hz、满摆幅为0.8 V的情况下,ADC有效位数(ENOB)达9.99位,信噪失真比(SNDR)为61.9 d B,无杂散动态范围(SFDR)为75.57 d B,总功耗约为1 m W,面积为0.069 mm~2。     

Stability Analysis of Periodic Orbits of Nonautonomous Piecewise-Linear Systems by Mapping Approach

In this brief, we present an exact stability analysis for periodic orbits of nonautonomous piecewise-linear systems. The described discrete-time maps are derived by connecting solutions at the switched points and solving relevant sets of linear differential equations. The coordinates of the switched points of the periodic orbit on each switching surface and the corresponding Jacobians are obtained. Theoretical analysis and simulation results for the piecewise-linear Duffing oscillator and Colpitts oscillator are presented to illustrate the proposed method.      

Canonical Asymetric Coupled-Resonator Filters

A direct (noniterative) procedure is presented for realizing canonical, structurally asymmetric lowpass prototypes for coupled-resonator bandpass filters with "bridge" couplings. An asymmetric prototype is obtained from the canonical symmetric prototype (which is realizable without matrix methods) by applying simple plane rotations to the coupling matrix. The resulting asymmetric prototype may he a more desirable structure, and may have fewer couplings, than the canonical symmetric prototype. The procedure is applicable to filters with symmetric or asymmetric frequency responses.     

Dual-Mode Canonical Waveguide Filters

This paper introduces a new form of dual-mode narrow-bandpass waveguide cavity filter. The filters, which can be constructed from either dual mode circular or square waveguide cavities, can realize the optimum transfer functions (including the exact elliptic function response). One of the unique features of these filters is that all the intercavity coupling irises may take the form of circular holes rather than long narrow slots. Several alternative input-output configurations are described. Experimental results on several filters indicate excellent agreement with theory.     

一种串行逐次逼近10位 D/A转换器

首先对几种形式的D/A转换器进行了比较,设计了一种电容型D/A转换器。这些电容在逐次逼近结构中构成二进制权阵列。这种结构的D/A转换器动态范围大、建立时间短,精度易于保证;且它的温度系数、电压系数、功耗及面积均优于电阻型D/A转换器。在Cadence SpectreS环境下进行仿真验证,该转换器信噪比为49 dB,积分非线性为±0.5 LSB。     

A Stochastic Approximation Approach to the Power-Control Problem

This paper proposes and analyzes a new distributed power-control algorithm based on the theory of stochastic approximation. The power-control problem is first converted into a stochastic approximation problem in which the zero point of a specific function is determined. A distributed power-control algorithm is then derived and its convergence properties are analyzed using standard techniques. In the distributed algorithm, each user iteratively updates its power level by using estimates of the inverse of the signal-to-interference ratio (SIR) of its channel. No knowledge of the channel gains or state information of other users is required. Moreover, the algorithm is robust in the sense that it can handle errors in the bit-error rate estimates, and hence, can be used in practical scenarios. Convergence of the algorithm is analyzed in the almost-sure sense     

A Polynomial Approximation Algorithm for Real-Time Maximum-Likelihood Estimation

Maximum-likelihood estimation subject to nonlinear measurement functions is generally performed through optimization algorithms when accuracy is required and enough processing time is available, or with recursive filters for real-time applications but at the expense of a loss of accuracy. In this paper, we propose a new estimator for parameter estimation based on a polynomial approximation of the measurement signal. The raw dataset is replaced by $n+ 1$ independent polynomial samples (PS) for a smoothing polynomial of order $n$, resulting in a reduction of the computational burden. It is shown that the PSs must be sampled at some deterministic instants and an approximate formula for the variance of the PSs is also provided. Moreover, it is also proved and illustrated on three examples that the new estimator which processes the PSs is equivalent to the standard maximum-likelihood estimator based on the raw dataset, provided that the measurement function and its first derivatives can be approximated with a polynomial of order $n$. Since this algorithm proceeds from a compact representation of a measurement signal, it can find applications in real-time processing, power saving processing, or estimation based on compressed data, even if this latter field has not been investigated from a theoretical perspective. Its structure which is made up of several separate tasks is also adapted to distributed processing problems. Because the performance of the method is related to the polynomial approximation quality, the algorithm is well suited for smooth measurement functions like in trajectory estimation applications.      

二极管方程新的解析近似解

提出了二极管方程一种新的解析近似解。使用精确的一阶及二阶微分和改进的牛顿-拉夫森方法,推导出一个简洁的二极管方程解析近似解。较之先前的二极管方程解法和近似,该解析近似解显著提高了二极管电流计算的精度和效率。同时,用户在将MOSFET模型如ACM、EKV和BSIM5中的二极管模型和反型层电荷模型实现到诸如SPICE等电路仿真模拟器中时,该解析近似解提供了高精度和高效率的计算方法。